| Cortical | Cortical-subcortical | Subcortical-nonsegmental | Segmental | Peripheral | |
| EEG | Variable; some with grossly visible epileptiform discharges and slow waves | Generalized spike and wave | No consistent findings | Normal | Normal |
| EMG | Bursts typically <75 ms | Bursts <100 ms | Variable burst duration | Bursts typically >100 ms | Variable burst duration; irregular periodicity of discharges is typical |
| Back-averaged EEG time-locked to EMG | Time-locked correlation almost always present; focal sharp wave 10 to 40 ms before myoclonic jerk is common | Time-locked correlation is typical | No association | No association | No association |
| SEPs | Enlarged cortical component in many cases | Enlarged cortical component possible | Normal | Normal | Normal |
| Long latency EMG reflex response | Variable; enhanced long latency reflex (C reflex) typical with cortical reflex myoclonus | Some cases have C reflex at rest | Some cases have reflex response to sound | Variable; some are very short latency and incompatible with supraspinal origin | Normal |
